Radio-frequency tank circuit



July 4, 1950 J. D. REID 2,514,337

RADIO FREQUENCY TANK CIRCUIT Filed Jan. 11, 1949 l INVENTOR. JOHN D RE/D.

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Patented July 1, 1950 RADIO-FREQUENCY TANK CIRCUIT John Drysclale Reid, Cincinnati, Ohio, assignor to Avco Manufacturing Corporation, Cincinnati, Ohio, a corporation of Delaware Application January 11, 1949, Serial No. 70,332

1 Claim.

The present invention relates to oscillatory circuits and specifically to a compact radio frequency tank circuit which has low inductance and high capacity and is particularly adapted for use in conjunction with very high frequency oscillators.

It is an object of the invention to provide a tank circuit unit which may be rapidly and economically constructed in actual commercial practice, dispensing with costly terminals in particular and minimizing the required number of connections.

In accordance with the invention there is provided a radio frequency tank circuit unit comprising a novel arrangement of tubular dielectric form, an inductor secured to the form, and capacitance means including plates disposed on the form.

For a better understanding of the present invention, together with other and further objects, advantages, and capabilities thereof, reference is made to the following detailed description of the accompanying drawings, in which there are specifically shown two preferred illustrative very high frequency tank circuit units incorporating the invention.

In the drawings:

Fig. 1 is a circuit schematic of a conventional Colpitts type oscillator for which my improved tank circuit is particularly suitable;

Fig. 2 is a typical prior art tank circuit arrangement for such an oscillator;

Figs. 3 and 4 are front and sectional views of a preferred tank circuit unit in accordance with the invention; and

Figs. 5 and 6 are front and sectional views of a modified form of tank circuit unit in accordance with the invention.

Referring now specifically to Fig. 1, there is shown a conventional Colpitts type oscillator circuit which is well-known to those skilled in the art, including an electron tube I l of the triode type, a grid capacitor l2, a plate capacitor l3, a plate load resistor 14, an inductor l5 between grid and plate, and a pair of capacitors l6 and H, capacitor l6 being connected between grid and cathode and capacitor I! being connected between plate and cathode. Capacitors I6 and I1 and inductor l5 comprise a conventional frequency-determining tank circuit, the operation of which is fully understood in the art. A grid resistor I0 is also provided.

Referring to Fig. 2, the conventional tank circuit arrangement (indicated symbolically by the circuit elements to the left of the dashed line in Fig. 1) is shown. Such conventional arrangeinent includes an insulated form 9 on which the inductor i5 is wound, and the usual separate capacitors I6 and I1, each of which may comprise plates coated or otherwise disposed on a ceramic form.

It will immediately be apparent that the construction shown in Fig. 3 has the following advantages:

(l) The separate coatings corresponding to the ungrounded plates of capacitors l6 and I! are omitted;

(2) The connections I8 and 8 between the inductor and those ungrounded plates are also omitted;

(3) Two forms are entirely dispensed with.

Referring now to Fig. 3 of the drawings, there isshown a tank circuit unit provided in accordance with the invention. It comprises a dielectric tube l9 which may be made of ceramic material coated with metal on the inside and on the outside. The metal 20 on the inside has a split tubular form. The split or longitudinal slot prevents the plate 20 from forming a closed turn. This metal coating 20 is connected to ground or cathode as indicated by the connections 2| and 22. The coating may conveniently be brought around one edge of the ceramic form as noted. The metal on the outside is provided by a plated conductive strap 23 wound around the dielectric tube in such a manner as to form an inductance. The capacitance formed by the outside spiral 23 adjacent to terminal 24 and the inside plate 20 corresponds to the capacitor [6, for example. The capacitance formed between the outside spiral 23 adjacent to terminal 25 and the inside plate 20 corresponds to capacitor [1, for example. The outside spiral 23 corresponds to the inductance l5 and when connected in the oscillator circuit shown, a point near its center will be at ground potential thus dividing the capacity to plate 20 which is at ground into two parts, corresponding to capacitors l6 and l! in Fig. 2. Leads, straps, or terminals 24, 25 are soldered to the ends of the winding 23 as indicated at 26.

Referring now specifically to Figs. 5 and 6 of the drawings, the modified form of the invention there shown comprises an inductor 28 having integral leads 29 and 30 bent around the periphery of ceramic tube 3| and soldered to spaced coated plates 32 and 33 on the outside of the tube. A common grounded plate is provided by a coating 34 which extends through the inside of the tube and is brought outside and grounded at 35.

In either embodiment permeability tuning may be provided in a conventional manner, as shown in Harvey U. S. Patent 2,180,413 or Kirk et al. U. S. Patent 2,221,217, for example.

It will be realized by those skilled in the art that various changes and modifications may be made therein without departing from the true scope of the invention as defined by the appended claim.

Having fully described and disclosed my invention, I claim:

In a Colpitts oscillator the combination of an electron tube having anode and cathode and grid electrodes; a tank circuit unit comprising: a hollow dielectric tubular support member, a split metallic plate deposited on the interior of said support member, means for effectively connecting said plate to said cathode, an inductor wound on the exterior of said support member and ineluding leads adapted to be coupled to said anode the remaining portion of said inductor providing capacitance between said anode and said cathode, said inductor and said capacitances constituting the frequency-determining circuit of said oscillator; and capacitive means for individually coupling said leads to said anode and grid electrodes.

JOHN DRYSDALE REID.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,251,631 Mayer Aug. 5, 1941 2,403,349 Dolberg July 2, 1946 FOREIGN PATENTS Number Country Date 242,768 Great Britain Nov. 19, 1925 

